Facebook Android SDK 3.19.1

Summary:
    see https://developers.facebook.com/android/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/android/upgrading/
Facebook Android SDK 3.20

Summary:
    see https://developers.facebook.com/android/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/android/upgrading/
Facebook Android SDK 3.20

Summary:
    see https://developers.facebook.com/android/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/android/upgrading/
Facebook Android SDK 3.21

Summary:
    see https://developers.facebook.com/android/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/android/upgrading/
Facebook Android SDK 3.21.1

Summary:
    see https://developers.facebook.com/android/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/android/upgrading/
release
Upgraded Gradle to 2.2.1 and Android Gradle Plugin to 1.0.0
Fixed Broken Link

Fixed Broken Link
Update build.gradle
Merge pull request #407 from vivekkiran/master

Upgraded Gradle to 2.2.1 and Android Gradle Plugin to 1.0.0